Detecting the oceanic CO2 sink today and in the future

May 28, 2014
Projections of annual oceanic CO2 uptake as simulated by five Earth system models plotted against surface pCO2 (bottom x-axis) and time (top x-axis).

The ocean has steadily taken up excess anthropogenic CO2 from the atmosphere but a slow down is expected in various parts of the ocean. The current observational network needs to be improved to monitor these changes.

The surface partial pressure of CO2 (pCO2) can be directly measured and is an indicator of long-term climate change and the ocean carbon uptake. A new study at the Bjerknes Centre for Climate Research aims to quantify the long-term growth rate of surface pCO2 over various large-scale ocean domains.

Using latest collection of pCO2 data and state-of-the-art Earth system models, the researchers led by Jerry Tjiputra (Uni Research), confirm that the ocean pCO2 has steadily increased following the atmospheric CO2 concentration in the past four decades. A large portion of this increase is attributed to the ongoing invasion of anthropogenic CO2 into the ocean, whereas increase in sea surface temperature contributes only marginally.

It is evident from the models that in order to monitor the oceanic CO2 sink accurately, long-term records of surface pCO2 in key ocean regions are required. The study shows that, despite substantial increase in number of measurements in the past years, only few ocean regions have a sufficient spatial and temporal coverage, namely the subtropical North Atlantic and the western subpolar North Pacific. For the rest of the ocean, particularly in the southern hemisphere, poor data coverage hinders the full picture of the pCO2 trend. The vast ocean area and the high cost of data collection are the main reasons for the data limitation.

The models, which were assessed in the IPCC-AR5, predict that the ocean will continue to absorb the emitted anthropogenic CO2 toward the end of the 21st century under a high-CO2 future scenario. However, the uptake rate is expected to change in critical regions, such as the subpolar North Atlantic, eastern equatorial Pacific, and the Southern Ocean. Detecting these changes will further elucidate the mechanistic response of ocean biogeochemistry to as well as its potential feedback to the climate.

Explore further: Southern Ocean is less efficient at exporting carbon than thought

More information: Tjiputra, J. F., Olsen, A., Bopp, L., Lenton, A., Pfeil, B., Roy, T., Segschneider, J., Totterdell, I., and Heinze, C., "Long-term surface pCO2 trends from observations and models," Tellus B, 66, 23083,2014.

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1 / 5 (2) Jun 02, 2014
The problem I and many others have with studies such as this is that they use many models with scanty data to produce these models and when they fail to predict what is observational happening they (scientists) continue to forecast way into the future what will happen. From the article it is admitted and recognized more data is needed. How can accurate assessments be made from incomplete data sets. They can't and that is why I and many other people that study climatic records and other scientific articles are not convinced that AGW is the main cause o9f global warming.
5 / 5 (1) Jun 02, 2014
Well, lets talk about that a little then. First of all, the idea of oceanic absorption of atmospheric CO2 is not a model, it's physics. Furthermore, observations of ocean acidity confirm that, in fact, the oceans are absorbing huge amounts of carbon. SO it seems that theory and observation match.
Models are used in this instance not to confirm acidification, they are used to estimate the point where the ocean's absorption begins to slow down. That is, the point at which it can not longer take up the amount of CO2 it has been taking up to date. This particular aspect has no affect on current understanding of what is happening around the planet because of the additional CO2 being added.
The article admits that measurements of the ocean in "specific areas" is lacking, and this might affect our understanding of the rate of change in CO2 absorption in those areas. It is the old fallacy - just because we don't know everything doesn't mean we know nothing.
5 / 5 (1) Jun 02, 2014
It is also the case that modelling and forecasting are necessary because we can't find that wormhole that allows us to see what is actually happening in 100 years. But, to quote my grandfather, when you see the canary drop off the perch, you don't hang around to see if it was just a heart attack. If it was the case that there was great disagreement between the different models trying to project what is likely to occur because of what we are doing, then your argument might have some weight. Yet, that is not the case. Remember that there is a difference between "projection" and "prediction".
Finally, I take issue with you on your comment "why I and many other people that study climactic records" because most people who study climatic records are acutely aware of the sudden, dramatic, 20th century temperature rise. Perhaps you can clarify what evidence would convince you?

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